The subject invention is generally directed to multiple port power directing circuits known as circulator circuits, and is directed more particularly to a relatively broad band lumped-element circulator circuit.
Circulator circuits are commonly utilized in microwave systems for directing microwave power between the components of a microwave system. For example, in radar systems, circulators are used to couple a transmission signal to the radiating antenna and to direct any signals that are received by the same antenna to the receiver while also maintaining isolation between both functions.
Present circulators used in microwave integrated circuits for microwave frequency operation include ferrite microstrip designs. A consideration with ferrite microstrip designs include size, particularly for phased array modules.
Known circulators also include those known as "lumped-element" circulators which have reduced size, relative to ferrite microstrip circulators, at microwave frequencies. However, the operating bandwidth of known lumped-element circulator designs at microwave frequencies are significantly less than that of ferrite microstrip circulators.
The following references disclose microstrip circulators and lumped-element circulators:
1. "On Stripline Y-Circulation at UHF," H. Bosma, IEEE Transactions on Microwave Theory & Tech., Vol. MTT-12, pp 61-72, January 1964.
2. "Lumped Element Y Circulator," Y. Konishi, IEEE Transactions on Microwave Theory & Tech., Vol. MTT-13, pp 852-864, November 1965.
3. "Resonance Isolator and Y-Circulator with Lumped-Elements at VHF," J. Deutsch and B. Wiesser, IEEE-Transactions on Magnetics, Vol. MAG-2, pp 278-282, September 1966.
4. "A Compact Broad-Band Thin-Film Lumped-Element L-Band Circulator," R. H. Knerr, IEEE Transact-ions on Microwave Theory & Tech., Vol. MTT-18, pp 1100-1108, December 1970.
5. "An Improved Equivalent Circuit for the Thin-Film Lumped-Element Circulator," R. H. Knerr, IEEE Transactions on Microwave Theory & Tech., Vol. MTT-20, pp 446-452, July 1972.
6. "A 4-GHz Lumped-Element Circulator," R.H. Knerr, IEEE Transactions on Microwave Theory & Tech., Vol. MTT-16, pp 150-151, March 1973.
7. "Wideband Operation of Microstrip Circulators," Y. S. Wu and F. J. Rosenbaum, IEEE Transactions on Microwave Theory & Tech., Vol. MTT-22, pp 849-856, October. 1974.
8. "Bidirectional Thin-Film Lumped Element Circulator," M. Kitlinski, Electronic Letters, Vol. 10, No. 6, 1974.
9. "The Frequency Behavior of Stripline Circulator Junctions," S. Ayter and Y. Ayasli, IEEE Transactions on Microwave Theory & Tech., Vol. MTT-26, pp 197-202, March 1978.
10. "Broad-Band Stripline Circulators Based on YIG and Li-Ferrite Single Crystals," E. Schloemann and R. E. Blight, IEEE Transactions on Microwave Theory & Tech., Vol. MTT-34, pp 1394-1400, Dec. 1986.
11. "Circulators for Microwave and Millimeter Wave Integrated Circuits," E. F. Schloemann, Proceedings of the IEEE, Vol. 76, pp 188-200, Feb. 1988.
12. "Multiport Lumped Element Circulators," M. Kitlinski, Technical University of Gdansk, Telecommunications Institute 80-852 Gdansk, Majakowskiego 11/12, Poland.